Space station around the whole planet

[korniton]

Did anyone ever try to build a Station around the whole planet? I mean, a circle station around kerbin? It would be like a million parts but maybe around a smaller one?

[DerekL1963]

37 minutes ago, korniton said:

Did anyone ever try to build a Station around the whole planet? I mean, a circle station around kerbin? It would be like a million parts but maybe around a smaller one?

I don't think there's a non-asteroid body you could encircle with a station and stay inside the game's physics limits.

[Gargamel]

The lack of station keeping would prevent you from assembling it in orbit anyways.  Eventually it would rotate so one end was inside the atmosphere while you were trying to launch the next section. 

[SpacedCowboy]

Jumpin' the shark ?  Yes ,,, but so "Kerbal"!

[Hans Dorn]

There might be some wobble.

[The Aziz]

3 hours ago, Hans Dorn said:

There might be some wobble.

Nothing that a bunch of struts can't fix

BUT!

With that physics bubble extender I've heard about, wouldn't it be possible to at least cheat such ring around OPM's moon Hale? This little blob is only 6km in diameter, so maybe there? I don't know of existence of a smaller body, this one looks like it's the perfect test subject.

I know there are problems about center of mass and all that, but did anyone actually tried?

[Zeiss Ikon]

Unless the ring is supported by a rigid structure from the parent body, it'll fall without active station keeping (or when the station keeping system runs out of fuel).

At some point, one side of the ring will be closer to the parent body than the other; it'll get more gravity pull, which will make it fall closer, increasing the gravity effect on that side (and decreasing it on the other) -- and the side that first got closer to the parent body will contact the body.  This is called a "crash" in common language.

There's a good reason Larry Niven (about forty years before KSP hit version 1.0) put attitude jets (Bussard ramjets burning the solar wind) on the Ringworld -- watching a spin-gravity ribbon around a star fall into the photosphere with a transverse velocity of around 1400 km/s would make for some serious eye candy, but you wouldn't want to be in the neighborhood when it happens...

[GrouchyDevotee]

I'm looking to upgrade my console...

Which MOD allows for the creation of a Dyson Sphere?

[wumpus]

On 3/17/2018 at 9:06 AM, Zeiss Ikon said:

There's a good reason Larry Niven (about forty years before KSP hit version 1.0) put attitude jets (Bussard ramjets burning the solar wind) on the Ringworld -- watching a spin-gravity ribbon around a star fall into the photosphere with a transverse velocity of around 1400 km/s would make for some serious eye candy, but you wouldn't want to be in the neighborhood when it happens...

Didn't keep the MIT students from chanting "the Ringworld is unstable" about 20-30 years ago at whatever con happened after somebody did the calculations.

As far as building something like that in KSP, I don't think KSP would like something extended through the physics bubble.  I also don't think that any procedural part would save from the issue of "things violating the physics bubble" and "too many parts".  *Something* involved would summon the Kraken: you are abusing Unity too badly.

[DerekL1963]

59 minutes ago, wumpus said:

Didn't keep the MIT students from chanting "the Ringworld is unstable" about 20-30 years ago at whatever con happened after somebody did the calculations.

That con was in 1971 after Ringworld was published (1970) but before Niven retconned the attitude control jets into existence in Ringworld Engineers (1980).  (I think some of the later editions of Ringworld were edited to add references to them as well.)

[suicidejunkie]

On 3/17/2018 at 9:06 AM, Zeiss Ikon said:

Unless the ring is supported by a rigid structure from the parent body, it'll fall without active station keeping (or when the station keeping system runs out of fuel).

At some point, one side of the ring will be closer to the parent body than the other; it'll get more gravity pull, which will make it fall closer, increasing the gravity effect on that side (and decreasing it on the other) -- and the side that first got closer to the parent body will contact the body.  This is called a "crash" in common language.

 

That's not how gravity works.

As your ring goes off-center, parts of it will be closer to the parent body, but that also means more than half of the ring is on the other side to get pulled back.  This cancels out as long as your struts keep your ring circular.

However, it also doesn't have a restoring force, so it'll drift around freely until it does hit something, hence the need for station keeping thrusters.

 

You may have problems with KSP trying to calculate the orbit based on center of mass of the two bodies and division by zeros may entice the Kraken to take up hula hooping.

Edited March 21, 2018 by suicidejunkie
Misinterpreted geometry

[OHara]

2 hours ago, suicidejunkie said:

As your ring goes off-center, parts of it will be closer to the parent body, but that also means more than half of the ring is on the other side to get pulled back.  This cancels out as long as your struts keep your ring circular.

Spheres have this neat cancellation, but is that true for rings? 
I haven't been able to compute a tidy result for a ring, but it seems the closer side is pulled harder, net, even accounting for its being shorter.

2 hours ago, suicidejunkie said:

You may have problems with KSP trying to calculate the orbit based on center of mass of the two bodies and division by zeros may entice the Kraken to take up hula hooping.

At first I thought that KSP computed the force of gravity for each part in a craft, but testing it on a pendulum satellite, I see that KSP computes gravity at the center-of-mass of the whole craft, and applies the same accelleration to each part.   That is, a single satellite does not feel tidal forces; but un-docked satellites rattling around in the cargo-bays of a long pendulum mother-ship satellite, do pull the mother-ship to point radially.  So building a ring around Gilly would probably be very frustrating in KSP

[Cadet_BNSF]

Tape Gaming did a video where he made a ring around Gilly

[Zeiss Ikon]

6 hours ago, DerekL1963 said:

That con was in 1971 after Ringworld was published (1970) but before Niven retconned the attitude control jets into existence in Ringworld Engineers (1980).  (I think some of the later editions of Ringworld were edited to add references to them as well.)

You're correct.  By the mid-1970s, not only had Niven corrected the Earth's rotation (which he had reversed in the first edition of Ringworld), he made reference just after Lying stand-up guy had crashed on the Ringworld to faint jets visible at several  locations along the edges of the ring.  These appear in my paperback copy, 7th printing (1975).

5 hours ago, suicidejunkie said:

That's not how gravity works.

As your ring goes off-center, parts of it will be closer to the parent body, but that also means more than half of the ring is on the other side to get pulled back.  This cancels out as long as your struts keep your ring circular.

However, it also doesn't have a restoring force, so it'll drift around freely until it does hit something, hence the need for station keeping thrusters.

You're incorrect.  See above about MIT students having calculated in 1971 that the Ringworld was unstable.  The net gravitational force by/on a spherical shell for any body inside is zero, but a narrow ring doesn't have this property because its surface is effectively one-dimensional rather than two-dimensional -- this prevents the cancellation of nearer by broader that occurs in a spherical shell.  I'm not qualified to do the integration required to calculate this for even a true zero-width, zero-thickness "one dimensional" ring, never mind for a ring with appreciable thickness and width, but I've been well satisfied that you must have a (gravitationally) complete spherical shell for the cancellation effect to be complete -- even a couple good-sized holes at opposite poles (as, for instance, to allow access to the interior of your Dyson Sphere) will result in small, but non-zero gravitational effects (generally, a weak attraction toward the inner surface at the equator between the two holes).

The "spherical shell with holes" is just an extreme case of a Ringworld -- and if there's any net gravitational force within a perforated spherical shell, it'll be greater the larger the holes relative to the size of the sphere.  A ribbon like the Ringworld, then, is just a spherical shell with really big holes at the poles, and there'll be an unavoidable net attraction toward the inner surface of the ribbon for anything inside the ribbon and close to its "equatorial" plane.

Even a complete spherical shell wouldn't be "stable" around a star -- there's no net unbalancing force, but there's no net restoring force, either, so the tiniest net momentum applied the the shell will eventually cause it to drift into contact (or close enough to burn through the shell) without active stabilization, essentially "pushing the star back to center" on an ongoing basis.